Nginx стал крашится практически ровно через каждые 5 часов
systemd[1]: nginx.service: Main process exited, code=dumped, status=11/SEGV
systemd[1]: nginx.service: Killing process 9209 (nginx) with signal SIGKILL.
systemd[1]: nginx.service: Killing process 9209 (nginx) with signal SIGKILL.
systemd[1]: nginx.service: Failed with result 'core-dump'.
You've run into a bug in perl 5.30, the version used in Ubuntu 20.04 LTS. The bug has been fixed upstream but that fix has not yet been backported to Ubuntu.
If you haven't got a need to run Perl code inside nginx (as most people do not) then you can uninstall the package libnginx-mod-http-perl and restart nginx to avoid the problem. This package was pulled in by the virtual package nginx-extras but most people don't actually run perl in the web server and so don't need it.
Юрий, вместо nginx-extras можно установить другой мета-пакет, например nginx-full или nginx-core. Certbot на нгинксовскую либу вряд ли завязан - его же можно и в standalone-режиме использовать.